I would really appreciate if anyone could shed some light on my issue. Premiere CC keeps randomly crashing to a black screen, the system remains on but nothing on the screen - this can happen 1+ hours into a session or after 10 minutes. A low memory warning sometimes comes up and at other times there is static coming from the speakers. I'm not sure what the issue is but I'm suspecting my graphics card.

The problem got worse as my project got more complicated. Its a five minute travel video that is now completely color corrected, warp stabilizer is used on some clips, numerous timelapses, all clips are 1080p (.mov and .mts), multiple tracks etc. It is really annoying now as I've nearly finished but premiere keeps crashing so I have to constantly save while working and restart my computer if it crashes.
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System info:
Windows 10 (up to date)
i7 6700k @ 4.0GHz (not overclocked)
16 GB DDR4 2130MHz (Premiere is given 12gb)
Gigabyte z170m-D3h-cf mobo
R9 390 (Drivers up to date)
Ocz-arc 225gb ssd
931gb 7200rpm seagate
500watt psu
Asus 4k monitor 60hz
Benq 1080p 60hz
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Scenarios I've thought about:

1) The graphics card isn't on the adobe list of supported graphics cards the R9 390 isn't actually there, however I've read various posts about this card not being an issue with openCL. Does anyone have a definitive answer here? Have I just got a card that will do this?

2) The low memory warning that comes up sometimes confuses me as this will happen with only premiere running. I have 16gb ram and have made sure to give premiere the majority of this. On top of that I have 70gb free on by c drive - where premiere is installed and my project files are located. From what I can see this shouldn't be causing me an issue.

3) My other thought is that the PSU isn't big enough for the system, would this explain the system crashing like this? or would a PSU problem result in the entire system shutting down?

Does anyone have any insight? Am I missing something, I don't really want to buy new hardware unless I have to as I purchased this system only 6 months ago.